I'm guessing your barrel has a gas block diameter of 0.625"...not 0.0625". A .750" gas block wont fit, obviously...nothing you can do to make it fit. I don't know what "drill .750 on the barrel" means. Just go buy a 0.625" gas block.
I build a lot of AR's and what you are asking is not very clear... .750 is 3/4 of an inch that would be a mighty big hole to drill in a barrel.
Normally .625 and .750 relate to outside diameter of a barrel. So it would be impossible to drill an OD .625 to .750. It would be possible to turn down a .750 OD to a .625 although I would not recommend it..
Now if you are referring to a gas port hole size of .0625 and drilling it out to .075 then you might get close using a #48 drill bit that would get you to .0760
If you are thinking of drilling out a gas port hole be sure of why you are doing it...
Sorry for misunderstanding, yes, the gas port is at .625 on the 16" barrel have another barrel with a .750 gas port on my K9 12.5"barrel. was told it is .750 on the 16".
The gas block size is the diameter of the barrel at the gas port. They are made in different sizes. The gas port hole is much, much smaller. Just but the correct size for your barrel.
Sorry for misunderstanding, yes, the gas port is at .625 on the 16" barrel have another barrel with a .750 gas port on my K9 12.5"barrel. was told it is .750 on the 16".
Your gas port isn’t .625. That would be massive and unsafe. The gas port is the very tiny hole on the top of the barrel and can only be measured accurately using a pin gauge.
I think you are talking about the thickness of the barrel at the gas port. This is called the gas journal. .625 is a fairly common sizing as is .750. There is no way to make a .750 gas block fit on a .625 gas journal. Neither can you make a .625 gas block fit in a .750 journal (even by reaming it). You just need to buy the appropriate sized gas block for the diameter of your gas journal.
Of course you can. It's rather simple. First, a titanium (for strength-weight ratio and to save ounces, bro) collar with an ID of 0.625 and OD of 0.750 is milled out on a 5-axis Haas CNC. Then all you have to do is drill a gas port into it, in the EXACT location to match the gas port on the barrel. Next, you press fit the new titanium collar onto your barrel with the .625" gas journal (spending about an hour trying to precisely line up the two gas ports to ensure reliable gas flow...which is critical when you shoot 4 moa with XM193). Once the cryogenic treatment has been completed, you then have a new 0.750" gas journal to use your 0.750" gas block.
Sure, it going to cost about $700 in parts and labor, but I bet Wright Armory would be happy to do it for you.
Are you an idiot? Go buy a new .625" gas block for $45
Thank you all for your input. Called Rosco and told them my issue. Was told that all of their barrels are designed for a .750 gas block. My friend was the one that brought to my attention for the gas port hole, that send me down the rabbit HOLE. 16-inch Bloodline M4 Barrel.
